Patent application title: PROCESS FOR PREPARING AN ARYLALKYL COMPOUND

Abstract:

The invention relates to a process for preparing an arylalkyl compound,
which comprises contacting a feed comprising a bis(arylalkyl)ether with
hydrogen in the presence of a catalyst at elevated temperature.

Claims:

1. A process for preparing an arylalkyl compound, comprising contacting a
feed comprising a bis(arylalkyl)ether with hydrogen in the presence of a
catalyst at elevated temperature.

2. A process as claimed in claim 1, wherein the arylalkyl compound is
alkylbenzene and the bis(arylalkyl)ether is bis(phenylalkyl)ether.

3. A process as claimed in claim 2, wherein the alkylbenzene is
ethylbenzene and the bis(phenylalkyl)-ether is bis(phenylethyl)ether.

4. A process as claimed in claim 2, wherein the alkylbenzene is cumene and
the bis(phenylalkyl)ether is bis(cumyl)ether.

5. A process as claimed in claim 2, wherein the temperature is from 200 to
300.degree. C.

6. A process as claimed in claim 2, wherein the pressure is from 5 to 100
bar.

7. A process as claimed in claim 2, wherein the catalyst is a catalyst
containing a metal of Group 10 or 11 of the periodic table.

8. A process as claimed in claim 7, wherein the metal is at least one
selected from the group consisting of Cu, Pd, Pt and Ni.

9. A process as claimed in claim 3, wherein the bis(phenylethyl)ether is
bis(α,α-phenylethyl)ether.

10. A process as claimed in claim 3, wherein the bis(phenylethyl)ether is
a mixture comprising at least two ethers selected from the group
consisting of bis(α,α-phenylethyl)ether,
bis(α,β-phenylethyl)ether and
bis(β,β-phenylethyl)ether.

12. A process as claimed in claim 3, wherein the bis(phenylethyl)ether is
produced in a process in which ethylbenzene is used, and the prepared
ethylbenzene is recycled to said process in which ethylbenzene is used.

13. A process as claimed in claim 12, wherein the process in which
ethylbenzene is used contains steps of converting ethylbenzene into
ethylbenzene hydroperoxide, obtaining propylene oxide and 1-phenylethanol
from the ethylbenzene hydroperoxide and propylene, and converting the
1-phenylethanol into styrene.

14. A process for preparing an alkylene oxide and styrene, comprising:i)
oxidizing ethylbenzene into ethylbenzene hydroperoxide with oxygen
containing gas;ii) reacting the ethylbenzene hydroperoxide with an alkene
in the presence of an epoxidation catalyst to prepare alkylene oxide and
1-phenylethanol, wherein after step ii) a stream comprising the
1-phenylethanol and a further stream comprising a bis(phenylethyl)ether
are separated from the reaction mixture obtained in step ii); andiii)
converting the 1-phenylethanol thus separated into styrene using a
dehydration catalyst, wherein after step iii) a stream comprising the
styrene and a further stream comprising a bis(phenylethyl)ether are
separated from the reaction mixture obtained in step iii);wherein the
streams comprising a bis(phenylethyl)ether separated after steps ii) and
iii) are separately or together contacted with hydrogen in the presence
of a catalyst at elevated temperature resulting in ethylbenzene, and the
ethylbenzene thus obtained is recycled, optionally after further
purification, to step i).

15. A process as claimed in claim 14, wherein the bis(phenylethyl)ether is
bis(α,α-phenylethyl)ether.

16. A process as claimed in claim 14, wherein the bis(phenylethyl)ether is
a mixture comprising at least two ethers selected from the group
consisting of bis(α,α-phenylethyl)ether,
bis(α,β-phenylethyl)ether and
bis(β,β-phenylethyl)ether.

17. A process as claimed in claim 14, wherein the streams comprising a
bis(phenylethyl)ether contacted with hydrogen further comprise
1-phenylethanol, 2-phenylethanol and/or methylphenylketone.

18. A process as claimed in claim 14, wherein the alkene is propylene.

Description:

CROSS REFERENCE TO RELATED APPLICATION

[0001]This application claims priority to European Patent Application
number EP 07114409.1 filed Aug. 16, 2007, the entire disclosure of which
is herein incorporated by reference.

FIELD OF THE INVENTION

[0002]The present invention relates to a process for preparing an
arylalkyl compound.

BACKGROUND

[0003]An example wherein an arylalkyl compound is used as a valuable
starting material, is a process for the coproduction of propylene oxide
and styrene wherein the arylalkyl compound started from is ethylbenzene.
Such process is herein also referred to as Styrene Monomer/Propylene
Oxide (SM/PO) process. In general such SM/PO process involves the steps
of (i) reacting ethylbenzene with oxygen or air to form ethylbenzene
hydroperoxide, (ii) reacting the ethylbenzene hydroperoxide thus obtained
with propene in the presence of an epoxidation catalyst to yield
propylene oxide and 1-phenylethanol, and (iii) converting the
1-phenylethanol into styrene by dehydration using a dehydration catalyst.

[0004]During the dehydration of 1-phenylethanol to styrene, but also
during any of the preceding steps, several by-products in addition to
water are formed, such as oligomers of styrene, including dimers and
trimers of styrene, and bis(phenylethyl)ethers. Examples of dimers of
styrene are diphenylbutenes and diphenylbutanes. Examples of
diphenylbutanes are 2,3-diphenylbutane, 1,3-diphenylbutane and
1,4-diphenylbutane.

[0005]A major part of said bis(phenylethyl)ether by-products formed in the
dehydration of 1-phenylethanol to styrene, consists of
bis(α,α-phenylethyl)ether, which is assumed to result from
the reaction between two molecules of 1-phenylethanol. Another
bis(phenylethyl)ether normally formed in a substantial amount is
bis(α,β-phenylethyl)ether. Bis(β,β-phenylethyl)ether
is normally formed in minor amounts. The latter two
bis(phenylethyl)ethers are assumed to result from the reaction between 1-
and 2-phenylethanol and from the reaction between two molecules of
2-phenylethanol, respectively. The 2-phenylethanol is usually already
present in small amounts in the feed to the dehydration treatment. This
is predominantly the result of the preceding epoxidation step, wherein
beside the main products propylene oxide and 1-phenylethanol also some
2-phenylethanol and methylphenylketone are formed. Also in the oxidation
step some 1-phenylethanol, 2-phenylethanol and methylphenylketone are
already formed. Since the boiling points of 1- and 2-phenylethanol and
methylphenylketone are all very close, a distillation treatment will not
effect full separation.

[0006]The above-mentioned bis(phenylethyl)ethers together form a
substantial part of the so called residual fraction or heavy ends, i.e.
all components present in a stream having a boiling point which is higher
than the boiling point of 1-phenylethanol.

[0007]Said heavy ends comprising bis(phenylethyl)ethers may be obtained as
a stream in separating styrene and water from the reaction mixture
obtained after dehydration of 1-phenylethanol. Further, said heavy ends
may be obtained as a stream in separating 1-phenylethanol from the
reaction mixture obtained after epoxidation of propylene with the help of
ethylbenzene hydroperoxide.

[0008]Normally the heavy ends will contain 5 to 50 wt. % of
bis(phenylethyl)ethers, suitably 10 to 40 wt. %. As stated hereinbefore,
a substantial part of the bis(phenylethyl)-ethers is composed of
bis(α,α-phenylethyl)ether. The remaining part is composed of
bis(α,β-phenylethyl)ether with small amounts of
bis(β,β-phenylethyl)ether being sometimes present as well.
Other main components present in the heavy ends include 2-phenylethanol
(0-40 wt. %), 1-phenylethanol (0-20 wt. %), methylphenylketone (0-30 wt.
%) and oligomers of styrene including dimers and trimers of styrene (0-40
wt. %). Small quantities of other ethers, such as the ether reaction
product of 1-phenyl-ethanol and phenol, may also be present. The exact
quantities of each of these components is determined by the specific
reaction conditions and catalyst employed in the dehydration step as well
as by the product separation means applied after this dehydration step.
Beside these main components the remainder of the heavy ends, up to 100
wt. %, is formed by other compounds having a boiling point higher than
that of 1-phenylethanol.

[0009]Heavy ends comprising bis(arylalkyl)ethers, such as those as formed
in the course of the conventional SM/PO process, may be disposed of as
fuel and burnt in a boiler house. However, in this way relatively
valuable products are lost. It is beneficial if the valuable products
present in the heavy ends could be recovered or if the heavy ends could
be transformed into valuable products.

[0010]U.S. Pat. No. 2,929,855 discloses the hydrogenolysis of a
distillation residue by-product which may be a dehydration residue from
the manufacture of styrene, as obtained in dehydration of
methylphenylcarbinol (1-phenylethanol) to styrene. This hydrogenolysis
process requires a relatively high temperature of between about 400 and
700° C., preferably 500 to 600° C., and a pressure of above
about 500 p.s.i. (34 bar), preferably between about 2000 and 4000 p.s.i.
(between about 138 and 276 bar), which is a relatively high pressure.
U.S. Pat. No. 2,929,855 further discloses that said residue by-product is
first subjected to flash distillation under subatmospheric pressure,
whereafter the distillate obtained is subjected to hydrogenolysis.

[0011]In Example 4 of U.S. Pat. No. 2,929,855 said flash distillation
procedure is performed on a dehydration residue as referred to above. The
distillate obtained, the composition of which is not disclosed, was then
subjected to hydrogenolysis at a temperature of 600° C. and a
pressure of 3000 p.s.i. (207 bar), with hydrogen in a ratio of 8 pounds
per 100 pounds of distillate. For each 48 pounds of distillate subjected
to the procedure of said Example 4, only 8 pounds of ethylbenzene was
obtained, the remainder being benzene, toluene and residue. Therefore,
the yield of ethylbenzene based on the amount of feed was only 17%.

[0012]U.S. Pat. No. 2,929,855 does not disclose whether or not the
dehydration residue from the manufacture of styrene that may be
hydrogenolysed, contains any bis(phenylalkyl)-ether. Even if the residue
from U.S. Pat. No. 2,929,855 would have contained such ethers and these
would have been converted into ethylbenzene, then still there is ample
room for improvement over U.S. Pat. No. 2,929,855, both in view of the
high hydrogenolysis temperature and pressure required to effect
hydrogenolysis and in view of the low yield of desired arylalkyl
compounds such as ethylbenzene.

SUMMARY OF THE INVENTION

[0013]Thus, the present invention aims to provide an effective and
efficient process for converting bis(arylalkyl)ethers which may be
present in heavy ends streams, which streams may be obtained in the
course of the SM/PO process, into valuable products which could
preferably be reused in the same process wherein said ethers were formed,
thus increasing the overall yield of a desired final product, such as
styrene in the SM/PO process, thereby also lowering the amount of heavy
ends to be finally disposed.

[0014]Surprisingly, it has been found that where a feed comprising a
bis(arylalkyl)ether, such as a bis(phenylethyl)ether, is contacted with
hydrogen in the presence of a catalyst at elevated temperature, said
ether is converted into the corresponding arylalkyl compound at a high
yield. Such arylalkyl compound can then advantageously be used in a
process wherein it is a valuable starting material, such as ethylbenzene
in the SM/PO process.

DETAILED DESCRIPTION OF THE INVENTION

[0015]Accordingly, the present invention relates to a process for
preparing an arylalkyl compound, which comprises contacting a feed
comprising a bis(arylalkyl)-ether with hydrogen in the presence of a
catalyst at elevated temperature.

[0016]Within the context of the present application, the arylalkyl
compounds to be prepared are alkylated benzenes in which the alkyl
substituents are straight or branched alkyl substituents comprising 2 to
10 carbon atoms. A more preferred arylalkyl compound contains one or two
alkyl substituents. Most preferably, the arylalkyl compound contains only
one alkyl substituent.

[0017]Although mixtures of bis(arylalkyl)ethers corresponding to different
arylalkyl compounds can be employed, thereby yielding a mixture of
different arylalkyl compounds, a single type of ether compound is
preferred in order to be able to optimise the process conditions for this
specific compound.

[0018]Preferably, the arylalkyl compound is alkylbenzene and the
bis(arylalkyl)ether is bis(phenylalkyl)ether. Said alkylbenzene may be
isopropylbenzene (or cumene). In a case where said alkylbenzene is
cumene, the bis(phenylalkyl)ether may be bis(2-phenyl-2-propyl)ether,
also referred to as bis(cumyl)ether or dicumylether, and/or
bis(2-phenyl-1-propyl)ether and/or
(2-phenyl-1-propyl)(2-phenyl-2-propyl)ether.

[0019]Most preferably, said alkylbenzene is ethylbenzene and the
bis(phenylalkyl)ether is bis(phenylethyl)ether. Said
bis(phenylethyl)ether may be bis(α,α-phenylethyl)ether.
Further, it may be a mixture comprising at least two ethers selected from
the group consisting of bis(α,α-phenylethyl)ether,
bis(α,β-phenylethyl)ether and
bis(β,β-phenylethyl)ether.

[0020]In a case where the feed comprises a bis(phenylethyl)ether, such
bis(phenylethyl)ether may be produced in a process in which ethylbenzene
is used. In such case, the prepared ethylbenzene is preferably recycled
to said process in which ethylbenzene is used. More preferably, in such
case, the process in which ethylbenzene is used contains steps of
converting ethylbenzene into ethylbenzene hydroperoxide, obtaining
propylene oxide and 1-phenylethanol from the ethylbenzene hydroperoxide
and propylene, and converting the 1-phenylethanol into styrene. Where the
prepared ethylbenzene is recycled, it is preferably subjected to a
separation treatment to separate ethylbenzene from heavy ends and to
obtain purified ethylbenzene before recycling.

[0021]By recycling the ethylbenzene as prepared in the process of the
present invention to said first step of preparing ethylbenzene
hydroperoxide, the overall yield of styrene based on the amount of
ethylbenzene used to prepare the styrene (as e.g. in an SM/PO process),
is increased. With the present invention, increases of up to 2 wt. % are
achievable.

[0022]As is commonly known, the mechanism of hydrogenolysis involves the
breaking of a chemical bond in an organic molecule with the simultaneous
addition of a hydrogen atom to each of the resulting molecular fragments.
Without wishing to be bound by any theory, it is believed that the
conversion of the bis(arylalkyl)ether in the process of the present
invention mainly proceeds via a different mechanism. This will be
explained for a case where the bis(arylalkyl)ether comprises
bis(α,α-phenylethyl)ether,
bis(α,β-phenylethyl)ether and/or
bis(β,β-phenylethyl)ether. It is believed that said ethers are
first converted to styrene and phenylethanol which may be either
1-phenylethanol or 2-phenylethanol. Then the phenylethanol is dehydrated
into styrene and the styrene is hydrogenated into ethylbenzene. Thus, one
bis(phenylethyl)ether molecule advantageously yields two ethylbenzene
molecules.

[0023]In a case where the feed to the present process comprises a
bis(phenylethyl)ether, the feed may advantageously further comprise
1-phenylethanol, 2-phenylethanol and/or methylphenylketone. In such case,
the latter three compounds are also converted into ethylbenzene thereby
possibly further increasing the overall yield of styrene based on the
amount of ethylbenzene used to prepare the styrene (as e.g. in an SM/PO
process). It is believed that the latter conversions also proceed via
styrene as an intermediate.

[0024]Where the feed to the present process also comprises oligomers of
styrene, including dimers and trimers of styrene, these latter compounds
may also be converted into ethylbenzene in the present process thereby
possibly further increasing the overall yield of styrene based on the
amount of ethylbenzene used to prepare the styrene (as e.g. in an SM/PO
process).

[0025]In respect of the latter, it is noted that EP 1375458 discloses a
process wherein 2,3-dimethyl-2,3-diphenylbutane is converted into cumene
by hydrogenolysis in the presence of a catalyst. Further, EP 1375458
discloses that by hydrogenolysis cumyl alcohol can also be converted into
cumene. However, EP 1375458 does not disclose or suggest that
bis(arylalkyl)ethers, for example, bis(phenylalkyl)ethers, can be
converted into arylalkyl compounds in the presence of a catalyst. In the
only Example of EP 1375458, a solution containing 1 wt. % of
2,3-dimethyl-2,3-diphenylbutane is subjected to hydrogenolysis. Said
solution only contained 1 wt. % of said dimer and 99 wt. % of an
unidentified solvent.

[0026]Preferably, the catalyst to be used in the present process is a
catalyst containing a metal of Group 10 or 11 of the periodic table
(IUPAC Inorganic chemistry nomenclature, revised edition (1989)). More
preferably, said metal is at least one selected from the group consisting
of Cu, Pd, Pt and Ni. It is especially highly preferred to use a
copper-based catalyst. Suitable examples of such copper-based catalyst
are copper, Raney copper, copper-chromium, copper-zinc,
copper-chromium-zinc, copper-silica, copper-alumina, etc. Of said
copper-based catalysts, copper-alumina is most preferred in view of its
relatively long lifetime and its relatively high and stable catalyst
activity during that lifetime for the specific reaction of hydrogen with
a feed comprising a bis(arylalkyl)ether.

[0027]If used in a fixed-bed or trickle-bed mode, the catalyst may have
any shape and size conventionally applied in these types of operation.
Accordingly, the catalyst particles may be in the form of spheres,
trilobes, quadrilobes, cylinders and the like. Their size may vary within
the normal commercially useful limits.

[0028]The temperature to be applied during the present process should be
an elevated temperature which means a temperature above 150° C.
Preferably, the temperature is from 150 to 400° C., more
preferably 150 to 350° C., most preferably 200 to 300° C.

[0029]Preferably, the pressure in the present process is from 5 to 100
bar, more preferably 10 to 50 bar and most preferably 20 to 50 bar.

[0030]As a particular embodiment of the present invention, the catalyst is
reduced by hydrogen prior to use in the present process. As a
non-limiting illustrative example, the catalyst is crushed and sized into
e.g. 6-20 mesh particles. The catalyst is then introduced into a reactor
and slowly reduced by heating the catalyst particles to a temperature of
e.g. 150-250° C. at a rate of from 1 to 10° C.,
particularly from 1.5 to 5° C. per minute, while flowing 0.001 to
0.1, specifically 0.02-0.10 wt. % hydrogen in nitrogen at a rate of
1-200, specifically 2-30 l/h. The catalyst is allowed to reduce at
150-250° C. for 1-10 hours and then the hydrogen content in the
nitrogen is doubled every 1-5 hours until the gas is 1-10, specifically
2-5 wt. % hydrogen in nitrogen. Catalysts containing copper are
preferably reduced at a temperature of between 150-200° C. to
minimize sintering. The catalyst is reduced for a final one to five hour
period and then cooled while maintaining gas flow. After cooling, the
reactor is capped without allowing any air to enter and the gas flow is
stopped. The reactor is opened in a nitrogen filled environment. The
particles of reduced catalyst, prepared by the afore-mentioned procedure
may be loaded onto a reactor over a bed support, e.g. made of porous
plate/tray or screen, optionally in a nitrogen filled environment. The
reduced catalysts are sized and shaped to stay above the bed support.

[0031]Further, the present invention relates to a process for the
preparation of an alkylene oxide and styrene, comprising the steps of:

i) oxidizing ethylbenzene into ethylbenzene hydroperoxide with oxygen
containing gas;ii) reacting the ethylbenzene hydroperoxide with an alkene
in the presence of an epoxidation catalyst to prepare alkylene oxide and
1-phenylethanol, wherein after step ii) a stream comprising the
1-phenylethanol and a further stream comprising a bis(phenylethyl)ether
are separated from the reaction mixture obtained in step ii); andiii)
converting the 1-phenylethanol thus separated into styrene using a
dehydration catalyst, wherein after step iii) a stream comprising the
styrene and a further stream comprising a bis(phenylethyl)ether are
separated from the reaction mixture obtained in step iii);wherein the
streams comprising a bis(phenylethyl)ether separated after steps ii) and
iii) are separately or together subjected to a process for preparing an
arylalkyl compound as described above resulting in ethylbenzene, and the
ethylbenzene thus obtained is recycled, optionally after further
purification, to step i). That is to say, said streams comprising a
bis(phenylethyl)ether are separately or together contacted with hydrogen
in the presence of a catalyst at elevated temperature resulting in
ethylbenzene. All embodiments as described above in connection with the
process for preparing an arylalkyl compound, are also applicable to the
step in said process for the preparation of an alkylene oxide and styrene
wherein ethylbenzene is produced.

[0032]Preferably, the bis(phenylethyl)ether in the streams comprising a
bis(phenylethyl)ether separated after steps ii) and iii) is
bis(α,α-phenylethyl)ether, or is a mixture comprising at
least two ethers selected from the group consisting of
bis(α,α-phenylethyl)ether,
bis(α,β-phenylethyl)ether and
bis(β,β-phenylethyl)ether. In addition, preferably, these
streams comprising a bis(phenylethyl)ether contacted with hydrogen
further comprise 1-phenylethanol, 2-phenylethanol and/or
methylphenylketone.

[0033]Preferably, in the above process for the preparation of an alkylene
oxide and styrene, the streams comprising a bis(phenylethyl)ether
separated after steps ii) and iii) are separately or together subjected
to a flash distillation treatment, which is preferably performed under
reduced pressure, thereby yielding a flashed distillate (or overhead
stream) which is then subjected to the process for preparing an arylalkyl
compound as described above.

[0034]The alkene used in the above process for the preparation of an
alkylene oxide and styrene, is preferably an alkene comprising from 2 to
10 carbon atoms and more preferably an alkene comprising from 2 to 4
carbon atoms. Examples of alkenes that can be used include ethene,
propene, 1-butene and 2-butene, with which the corresponding ethylene
oxide, propylene oxide and butylene oxides can be prepared. Preferably,
the alkene is propylene.

[0035]The advantages of the above process for the preparation of an
alkylene oxide and styrene, wherein the ethylbenzene obtained by
contacting a stream comprising a bis(arylalkyl)ether with hydrogen in the
presence of a catalyst at elevated temperature, have already been
demonstrated above. Further information on performing the reactions of
steps i), ii) and iii) as such and the separations after step ii) and
after step iii) is given below.

[0036]In step i) of the above process for the preparation of an alkylene
oxide and styrene, ethylbenzene is oxidized into ethylbenzene
hydroperoxide with oxygen containing gas. For example, ethylbenzene
hydroperoxide can be prepared by the liquid phase oxidation of
ethylbenzene with air. Such oxidation processes are well known in the
art. An example thereof is described in U.S. Pat. No. 5,883,268.

[0037]Preferably, during the start-up phase of the oxidation reaction, a
small amount of an organic peroxide, such as ethylbenzene hydroperoxide
itself, is added as an initiator to the ethylbenzene. Preferably, during
the liquid phase oxidation of ethylbenzene, the ethylbenzene
hydroperoxide concentration in the ethylbenzene diluent is kept below 20
wt. % on the basis of the total weight of the reaction mixture. In
general, the liquid phase oxidation is carried out at a temperature of
from 50 to 250° C., suitably of from 100 to 200° C. The
pressure of the present process is not critical and can be chosen such as
to best accommodate specific circumstances. Generally, the pressure near
the top of the reactor vessel will be from atmospheric to 10*105
N/m2, more specifically from 1 to 5*105 N/m2. The reaction
mixture thus obtained is usually separated into a stream containing
ethylbenzene hydroperoxide dissolved in ethylbenzene wherein the
ethylbenzene hydroperoxide concentration may be from 20 to 50 wt. %, and
an ethylbenzene stream. Such separation may be effected by flash
distillation.

[0038]In step ii) of the above process for the preparation of an alkylene
oxide and styrene, the ethylbenzene hydroperoxide is converted into
methylphenylcarbinol (1-phenylethanol). This reaction is carried out by
contacting an alkene with the ethylbenzene hydroperoxide in the presence
of an epoxidation catalyst. The ethylbenzene hydroperoxide used is
dissolved, preferably in ethylbenzene as used in the preceding oxidation
step. In the epoxidation step a homogeneous catalyst or a heterogeneous
catalyst can be applied. As homogeneous catalysts molybdenum compounds
are frequently applied, while catalysts based on titanium on a silica
carrier are often used as heterogeneous catalysts. A preferred catalyst
comprises titanium on silica and/or silicate. Further preferred catalysts
are described in EP 345856. The reaction generally proceeds at moderate
temperatures and pressures, in particular at temperatures in the range of
from 25 to 200° C., preferably in the range from 40 to 135°
C. The precise pressure is not critical as long as it suffices to
maintain the reaction mixture as a liquid or as a mixture of vapour and
liquid. In general, pressures can be in the range of from 1 to 100 bar,
preferably in the range from 20 to 80 bar.

[0039]Between steps ii) and iii), a stream comprising the 1-phenylethanol
and a further stream comprising a bis(phenylethyl)ether are separated
from the reaction mixture obtained in step ii). This separation can be
effected in any way known to be suitable to someone skilled in the art.
For example, the liquid reaction mixture may be worked up by fractional
distillation and/or selective extraction. Preferably, the reaction
mixture is first distilled to produce an overhead stream comprising
alkylene oxide and a bottom stream comprising ethylbenzene,
1-phenylethanol and heavy ends (said heavy ends including
bis(phenylethyl)ethers), which latter bottom stream is then distilled to
produce an overhead stream comprising ethylbenzene and a bottom stream
comprising 1-phenylethanol and heavy ends, which latter bottom stream is
then distilled to produce an overhead stream comprising 1-phenylethanol
and a bottom stream comprising heavy ends. The latter bottom stream
comprising a bis(phenylethyl)ether is then preferably subjected to a
flash distillation treatment, thereby yielding a flashed distillate (or
overhead stream) which is then subjected to the process for preparing an
arylalkyl compound as described above.

[0040]In step iii) of the above process for the preparation of an alkylene
oxide and styrene, the 1-phenylethanol, once separated from the reaction
mixture obtained in step ii), is converted into styrene (and water) by
dehydration in the presence of a dehydration catalyst. The processes and
catalysts for the step of dehydrating 1-phenylethanol as described in WO
99/42425 and WO 99/42426, can be used. However, any other suitable
process or catalyst known to someone skilled in the art can in principle
be used.

[0041]The production of styrene by dehydrating 1-phenylethanol is well
known in the art. It can be carried out both in the gas phase and in the
liquid phase. Suitable dehydration catalysts include for instance acidic
materials like alumina, alkali alumina, aluminium silicates and H-type
synthetic zeolites. Dehydration conditions are also well known and
usually include reaction temperatures of 100-200° C. for liquid
phase dehydration and 210-320° C., typically 280-310° C.,
for gas phase dehydration. Pressures usually range from 0.1 to 10 bar.
For the purpose of the present invention gas phase dehydration is
preferred. The gas phase dehydration may be carried out at a temperature
in the range of 230 to 280° C. using an alumina-based dehydration
catalyst. By applying these relatively low temperatures for gas phase
dehydration the formation of bis(phenylethyl)ethers is promoted and the
formation of other high boiling components like oligomers of styrene,
including dimers and trimers of styrene, is limited. The increased amount
of bis(phenylethyl)ethers formed at the lower reaction temperatures can
then be converted into ethylbenzene in a process for preparing an
arylalkyl compound as described above.

[0042]After step iii), a stream comprising the styrene and a further
stream comprising a bis(phenylethyl)ether are separated from the reaction
mixture obtained in step iii). This separation can be effected in any way
known to be suitable to someone skilled in the art. For example, the
liquid reaction mixture may be worked up by fractional distillation
and/or selective extraction. Preferably, the reaction mixture is
distilled to first produce an overhead stream comprising the styrene and
water, which overhead stream is further worked up in order to obtain
substantially pure styrene, and a bottom stream comprising phenylethanol,
methylphenylketone and heavy ends (the latter including
bis(phenylethyl)ethers). Further, preferably, said bottom stream is
distilled to produce an overhead stream comprising the phenylethanol and
methylphenylketone, and a bottom stream comprising said heavy ends. The
latter bottom stream may then be subjected to a flash distillation
treatment, thereby yielding a flashed distillate (overhead stream) which
is then subjected to the process for preparing an arylalkyl compound as
described above.

[0043]The invention is further illustrated by the following Examples. In
the Examples, the following abbreviations are used:

[0044]Further, in these examples the yield of the desired arylalkyl
compound ethylbenzene (EB) is defined as the weight percentage of EB
formed relative to the total weight of the feed.

EXAMPLE 1

[0045]The following experiment was carried out in downflow in a bench
scale unit comprising a reactor connected to a heating/cooling system, a
high pressure feed pump, and two vessels (for incoming and outgoing feed
streams), and a gas inlet connected to sources of hydrogen and nitrogen.
180 g of a copper-chromium catalyst (3 mm*3 mm tablets) and 450 g of
inert silicon carbide particles (having a diameter of 0.2 mm) were added
to the reactor. The bed inside the reactor comprised said catalyst
particles and inert particles. Glass balls were added to fill the
remaining empty space above said bed. The glass balls had a diameter of 3
mm and were used to provide adequate fluid distribution. The volume ratio
of catalyst and inert particles to glass balls was about 95:5. The
section of the reactor containing the catalyst and inert particles and
glass balls had a cylindrical shape. The diameter of this cylindrical
section was 3.2 cm. The total height of the reactor was 50 cm.

[0046]Before introducing the feed, the reactor was first purged with
nitrogen under slight overpressure (1.3 barg). The reactor temperature
was then raised to 130° C. Hydrogen was introduced at a starting
concentration of 1% volume. Then the hydrogen concentration was gradually
increased to 100% volume at a rate such that the reactor temperature did
not exceed 170° C. The temperature was then raised to 175°
C. within 0.5 hour which temperature was maintained for 4 hours. The
foregoing procedure was used to activate (by reduction) the catalyst
before introducing the feed.

[0047]The feed used originated from a combination of two by-product
streams as produced in an SM/PO process. The first by-product stream was
produced in separating 1-phenylethanol from the reaction mixture obtained
in reacting ethylbenzene hydroperoxide with propylene. The second
by-product stream was produced as follows: (a) the reaction mixture
obtained in converting 1-phenylethanol into styrene and water was
distilled to first produce an overhead stream comprising the styrene and
water and a bottom stream comprising phenylethanol, methylphenyl-ketone
and heavy ends (the latter including bis(phenylethyl)ethers) and (b) said
bottom stream was distilled to produce an overhead stream comprising the
phenylethanol and methylphenylketone and a bottom stream comprising said
heavy ends.

[0048]Before using the feed, said combination of by-product streams was
first subjected to a flash distillation treatment at a temperature of
240° C. and a pressure of 60 mbara, thereby yielding a flashed
distillate which was then used as the feed and which had the composition
as shown in Table 1.

[0049]Just prior to introducing the liquid feed, the reactor temperature
was set to 180° C. and the reactor pressure was increased to 25
bar. Said pressure was constant for the remainder of the experiment. Said
feed, comprising bis(phenylethyl)ethers, was then fed to the reactor at a
rate of 50 g/hour, which corresponds to 0.3 g liquid/g catalyst/hours.
The hydrogen gas stream was fed at a rate of 12-15 liter/hour (normal
conditions).

[0050]The process was carried out in trickle-flow downflow mode, meaning
that both liquid phase and gas phase flowed concurrently downward through
the catalyst bed. No liquid reaction product was recycled to the inlet of
the reactor.

[0051]After the start of the feed of the liquid to the reactor, the
temperature was gradually increased from the starting temperature of
180° C. up to 260° C. in steps of 20° C. every 1 or
2 days. After 6 days a temperature of 260° C. was reached; the
temperature was then maintained at said level. Further, at several points
in time after said start, samples were taken from the reaction product.
For each of the samples, the yield of EB was measured by means of GC
analysis.

[0052]The experiment was performed continuously for 23 days. After 7 days
and at a temperature of 260° C., the yield of EB reached a maximum
of about 48%. This means that almost half of the weight of the feed was
converted into EB, which could then advantageously be recycled to the
first step in an SM/PO process, preferably after further purification of
the stream containing the EB. Such yield is considerably higher than the
yield of ethylbenzene, based on the amount of feed, of 17% as obtained in
Example 4 of U.S. Pat. No. 2,929,855 as discussed above. Further, after
15 days the yield of EB stabilized at an average level of about 30%.

EXAMPLE 2

[0053]The procedure of Example 1 was repeated. However, a copper-alumina
catalyst was used instead of a copper-chromium catalyst.

[0054]The experiment was performed continuously for 40 days. After 7 days
and at a temperature of 260° C., the yield of EB reached a maximum
of about 46%. This means that about the same weight fraction of the feed
was converted into ethylbenzene as in Example 1. However, after 15 days
the yield of EB stabilized at an average level of about 40%. This is
considerably higher than the yield of EB after 15 days as achieved in
Example 1 (which was only 30%).